RRC Connection Re establishment procedure During the RRC Connection Re establishment procedure, when UE sends an RRC Connection Re establishment Request to eNodeB , then based on what conditions RRC at eNodeB would decide to send either RRC Connection Reestablishment or RRC Connection Reestablishment Reject?. From where does the RRC gets information to decide?Answer 1:Pranab Tandon Resstablsihment is sent after following are found to be correct physCellId,shortMAC-I ,c-RNTI t and there are enough resources to cater to the coming UE(Admission Control).

RRC Connection Reestablishment Reject is sent when either value of the above are incorrect or admission control fails.

EnodeB already has the information ,for shortMAC-I it consults the PDCP layer for assess it's correctness.

Answer 2:Chetan Agrawal Hi, When UE sends RRC Connection Re-estabilishment request message with parameters ( shortMAC-I , physCellId ,,c-RNTI ) to eNB then eNodeB can send RRC Connection Re-estabilishment Reject message in few cases :

-> eNodeB RRC verify the shortMAC-I / C-RNTI / phyCellid values of UE . eNodeB has already these information . In case of incorrect shortMAC-I / C-RNTI / phyCellid values , eNodeB can send RRC Connection Re-estabilishment reject to UE. -> During RRC connection re-estabilishment procedure , if eNodeB RRC recieves failure response from RLC/MAC/PDCP protocol . In case of failure response , eNodeB can send RRC Connection Re-estabilishment reject to UE.

In case of correct shortMAC-I / C-RNTI / phyCellid values and successful response from MAC/RLC/PDCP protocol , eNB sends RRC Connection Re-estabilishment message to UE.

Answer 3:Shailesh chidrawar UE will start RRC connection re-establishment procedure when UE detects 1. Radio link failure 2. Handover Failure 3. RRC Connection Reconfiguration procedure fail 4. Integration failure indication by lower layer

Answer 4:Abinash Singh RRC CONNECTION REESTABLISHMENT REQUEST message consists of:-

UE-Identity: UE identity is included to retrieve UE context and to facilitate contention resolution by lower layers. The UE Identity shall be set as follows:

1. Set the C-RNTI to the C-RNTI used in the source PCell (In case of handover and mobility from E-UTRA failure) or used in the PCell in which the trigger for the re-establishment occurred (other cases); 2. Set the physCellId to the physical cell identity of the source PCell (handover and mobility from E-UTRA failure) or of the PCell in which the trigger for the re-establishment occurred (other cases); 3. Set the shortMAC-I to the 16 least significant bits of the calculated MAC-I

Re-establishmentCause: This IE indicates the failure cause that triggered the re-establishment procedure and shall be set as follows:

1. If the re-establishment procedure was initiated due to reconfiguration failure (the UE is unable to comply with the reconfiguration sent in RRC CONNECTION RECONFIGURATION), then set the reestablishmentCause to the value 'reconfigurationFailure'; 2. If the re-establishment procedure was initiated due to handover failure (intra-LTE handover failure or inter-RAT mobility from EUTRA failure) then, set the reestablishmentCause to the value 'handoverFailure' 3. Set the reestablishmentCause to the value 'otherFailure' if the re-establishment procedure was triggered due other causes than indicated in cases 1 and 2